Field of the Invention
The present invention relates to an image forming apparatus including a motor configured to rotate a rotary polygon mirror.
Description of the Related Art
Hitherto, in an image forming apparatus such as a copying machine and a printer, a laser optical system configured to emit a light beam from a semiconductor laser a rotary polygon mirror is widely used to form a latent image on a photosensitive member. It is known that a motor which rotates the rotary polygon mirror has a large inertia and therefore needs a long time to stabilize its rotation. Further, along with increase in speed of the image forming apparatus in recent years, the rotary polygon mirror is required to be rotated at an extremely high speed. Therefore, a long time is required for the motor to rise from a stopped state. Further, the high-speed rotation of the rotary polygon mirror has a problem of a noise caused by wind whistle and a problem in a reduced lifetime of the motor.
The image forming apparatus cannot start image formation unless the motor is in a stably rotating state. Therefore, first copy output time (or first print output time) is affected by the time required for the motor to rise.
In order to solve problems similar to those described above, in Japanese Patent No. H07-36600, there is disclosed a technology of adjusting a speed of the motor. Specifically, in Japanese Patent No. H07-36600, there is disclosed a technology of controlling, when transfer of recording data is started, the motor to rotate at a speed lower than a target rotation speed set for the image formation after turning ON a main power source, and then controlling the motor to rotate at a higher speed (the target rotation speed set for the image formation) in accordance with an instruction to start recording.
In a case where a user transmits image data (recording data) from an external information device such as a PC so that the image forming apparatus forms an image, the user inputs the instruction to start the image formation to the external information device. The image forming apparatus is desired to be able to form an image at the time of reception of the image data from the external information device or to transition to a state in which the image can be formed as soon as possible after the reception of the image data. After a step of rotating the motor at the rotation speed smaller than the target rotation speed set for the image formation in response to the reception of the image data from the external information device, the motor is controlled through a step of accelerating the motor so that the rotation speed of the motor becomes equal to the target rotation speed set for the image formation in response to the instruction to start recording. If the motor is controlled in the above-mentioned manner, there is a fear in that increase in start time of the motor may lead to increase in the first print output time.